Removal of SO₂ from Flue Gas by Sodium Humate Solution

A novel process of flue gas desulfurization (FGD) by sodium humate (HA−Na) solution was developed. Experiments were carried out to examine the effect of various operating parameters, such as the HA−Na concentration, pH, temperature, gas flow rate, O 2 concentration, SO 2 inlet concentration, and NO 2, on the SO 2 absorption efficiency and desulfurization time in a lab-scale bubbling reactor. The experimental results indicate that the HA−Na concentration significantly influences the desulfurization time but has little effect on the SO 2 absorption efficiency. The desulfurization time increases with the HA−Na concentration reaching 0.06 g/mL, and after this value, it begins to decrease. The SO 2 absorption efficiency maintains 99% when pH is above 4.5. A low gas flow rate and low temperature are favorable to SO 2 absorption. The increase of the SO 2 inlet concentration improves the mass transfer of SO 2 and accelerates the SO 2 consumption rate. NO 2 coexisting with SO 2 can promote SO 2 absorption because it may speed up oxidation of sulfite to sulfate. HA−Na solution shows great performance in SO 2 absorption, and the SO 2 absorption efficiency can be maintained above 98% for 1.5 h with 100 mL of HA−Na solution (0.06 g/mL), at the condition of 25 °C, gas flow rate of 0.14 m 3 /h, and inlet SO 2 concentration of 2000 ppm. Moreover, the desulfurization products can be made into the humic acid (HA) compound fertilizer, and recycling water can be obtained in this desulfurization process.